1. Field of the Invention
This invention relates to a method for artificially and rapidly forming patina on copper substrates, to products therefrom, in particular to such copper substrates as roofing and outside covering, and to new solutions for rapidly forming patina on copper.
2. Description of Related Art
Attempts have been made in order to obtain coloring of copper similar to patina on copper.
For instance in U.S. Pat. No. 1,951,304, dated Mar. 13, 1934, as invented by FREEMAN et al., is disclosed a method producing on the surface of copper and alloys thereof, an adherent green coloration patina by treating the copper or copper alloy with a solution of ammonium sulphate and thereafter exposing to oxygen. In some cases a color is developed which is darker green than that which develops by natural weathering.
In U.S. Pat. No. 2,587,216, dated Feb. 26, 1952, as invented by QUADRIO, is disclosed a method involving the following steps: dipping an object in a bath containing a solution of potassium sulfide, then a second bath of sulphuric acid, drying, then dipping in a third bath containing salt ammoniac, and then coating with shellac and a protective coating.
In U.S. Pat. No. 3,152,927, dated Oct. 13, 1964, as invented by MATTSON et al., is disclosed an agent for the artificial green patination of object comprising an aqueous sludge obtained by admixing an aqueous solution containing copper nitrate, iron sulphate and sodium hydroxide.
In U.S. Pat. No. 3,434,890, dated Mar. 25, 1969, as invented by ARONBERG, is disclosed a process for forming patina involving wetting a copper base alloy with a solution volatile water soluble organic solvent such as alcohol and salts of inorganic acids and primary amines.
In U.S. Pat. No. 3,473,970, dated Oct. 21, 1969, as invented by ROBEY, is disclosed a composition for imparting patina comprising copper sulphate, ammonium sulphate lithium chloride, sodium dichromate, hydrochloric acid, magnesium montmorillonite and water.
In U.S. Pat. No. 3,497,401, dated Feb. 24, 1970, as invented by HANSON et al., is disclosed a method for producing synthetic patina by immersion in an aqueous acidic solution with potassium chlorate and copper sulphate.
In U.S. Pat. No. 3,725,138, dated Apr. 3, 1973, as invented by JONES, is disclosed a patina produced on a copper surface by applying an aqueous acidic solution of ammonium sulphate, sulphamic acid and iron sulphate, drying the solution to form a film on the copper surface. The film is then reacted with the copper surface in a humid atmosphere at a temperature of at least 30.degree. C. for a period of time to form an adhered corrosion product of which a major portion is insolubilized. The soluble parts are then dissolved, thereby developing in the reaction product the color of natural patina.
In U.S. Pat. No. 4,416,940, dated Nov. 22, 1983, as invented by LOYE et al., is disclosed a two step process comprising first applying an opaque pigmented base coat containing a patina color producing colorant to a primed or unprimed substrate, curing the base coat, applying to the cure base coat a non-opaque top coat containing one or more copper color producing additives.